Disposable medical electrodes are used in cardiac monitoring by ECG. A disposable medical electrode for deriving electrical signals from a patient's skin is described in U.S. Pat. No. 3,977,392 (Eastprint Inc). The Eastprint electrode is intended to conform to the contour of the patient's body and to provide a good conductive path between a skin area underlying the electrode and an electrical contact in the form of a male snap fastener element projecting from the top of the electrode. A support layer in the form of a soft compliant layer of polyurethane foam has an aperture in which a gel pad is a compression fit. The lower face of the support layer is adhesive coated. The contact element and the foil strip are offset on the support layer with a flexible conductive foil strip connecting them so that movement of the contact element does not disturb the conductive path between that element and the skin area to which the electrode is adhered. The foil strip both makes the contact with the gel pad and provides the connection to the remotely located contact element, and for the former purpose it has to be unattacked by the gel material and to be electrically compatible with the gel pad, and so silver or other relatively expensive materials have to be used. Furthermore the Eastprint electrode is complex and inherently expensive to make, so that it would not be attractive for use in routine diagnostic procedures.
Recently 3M Health Care have introduced the socalled Littman diagnostic ECG electrode which uses a solid gel electrolyte on the lower face of aluminium foil. But a solid gel presents problems where it is necessary to make contact through the skin on a hairy chest, and requires a 20-30 second delay before the skin is penetrated and contact is established.